Making a connection: What to look for in broadcast cables

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Even in an increasingly wireless world, there’s no shortage of demand for high-quality cable. We hook up with cable specialists, VDC Trading, to find out why

No matter how efficient your camera, video and distribution system is, your production goes nowhere without the right cabling to transport and protect it. We take a look at the popular current cable systems with Camden based specialists VDC Trading, suppliers of Van Damme cable, Neutrik and OpticalCon assemblies to the broadcast industry.

Probably the largest consumers of professional cable in the industry are the outside broadcast trucks. Between the need for audio and video connections from sports grounds, concerts and public events to the truck and the transfer of the final mixes to and from commentary studios and out to satellite uploads, an OB truck can require several kilometres of cable. All of which must be one hundred per cent reliable or the whole system fails.

“For audio, most of the outside trucks and TV studios we supply use Van Damme Brown Series OB Transmission grade, pre-jacketed eight-way Starquad multicore via 26 pole Mil spec OB CON connectors,” explains VDC technician Adam Jafrabati. “Featuring an extremely tough polyurethane outer jacket, better than 90% coverage braided screens for high rejection of EMI and RFI and with overall diameters sized to suit the common outside broadcast multipins, these cables are built to excel in the most hostile of environments. I would prefer to see a more robust connector in common use but the OB CON is extremely light which is useful in an outside broadcast truck where weight is a factor.”

VDC Trading’s Paul Marchesi with an HMA cable

For the video links, some trucks at sporting events are still using Triax cable but most of the industry now uses HD Video cable with SD having become effectively redundant. HD cable is available in a number of varieties including low smoke for sensitive environments.

There is a range of multicore options for video too. The HD Vision range of 75 Ohm precision multicore coaxial cables comprises four and six-way PVC jacketed dynamic multicores. Great attention has been paid to their electrical characteristics and tolerances to ensure performance with SMPTE 292M HD-SDI signals as well as SDI and analogue video.

It is frightening thought that the success of your show might be down to a single soldered joint to a cable that you keep kicking as you cross the studio

There is also a growing trend towards the use of fibre optic cable thanks to its ability to carry huge amounts of information and channels. VDC Trading has expanded its production facilities to include a fibre optic clean room needed to construct and terminate fibre optic assemblies. For broadcast purposes, Van Damme Tourlight fibre optic cables are Tactical Single Mode and Multi-Mode fibre optic OS1 and OM3 deployable fibre cables for outside broadcast and robust studio floor or fibre infrastructure.

The cables are extremely robust, are available in an increasing number of variations and can carry huge amounts of information. Ideally connected by HMA expanding beam connectors, they can withstand the dirt and grime of the outside broadcast environment and the HMA connector is easy to connect as there is no male or female version. The expanding beam means that the signal at the connector is expanded to such a size that connection is always one hundred per cent. Easy to wipe clean or replace if necessary, the HMA connector is becoming a favourite solution to fibre optic connections in the field. One of these cable systems has been supplied to BBC Scotland recently by VDC and interest is growing amongst the OB community.

An engineer solders CAT 6 cables

These days, hybrid multicores are commonly adopted. Once only available in one or two formats, the hybrid cable can now be made to a huge range of specifications. A typical combination is eight channels of audio, two of HD video and two of CAT 6A data. Encased in a rugged outer sleeve, the hybrid can carry all the cabling requirements in one go. Specially built termination panels allow for a faster and simpler set up. These are becoming especially popular for the fast rigging of large video arrays in the live arena for concert broadcasts. They provide provision for network, HDTV distribution via HDMI Cat X converters, control signals and satellite broadcasts.

Reliability is everything in the world of cable. The loss of signal from a single cable can mean the failure of a live broadcast and often a time consuming hunt for the offending cable among many. At VDC a testing station (image below) is used to test every cable before it leaves the premises. Designed by the team at VDC, the testing station has a multitude of input and output connectors. A faulty connection causes the light on the top to flash and, yes, a loud siren to sound. It is a matter of pride amongst the staff to avoid the shame of a failed cable!

VDC Trading CEO Niall Holden summarises: “Despite the fact that it is frightening thought that the success of your show might be down to a single soldered joint to a cable that you keep kicking as you cross the studio, you can take heart that amongst the cable community we have people who care enough about it to make sure it’s up to the task.”